Posts: 91
Threads: 9
Joined: Feb 2010
City: Macon, GA
I picked up a Sansei AM / FM plastic table radio a while back. It's a cheap early 1960s six tube, two diode Japanese set that came with a few gremlins. So far, I have not found a schematic so all the repairs that I've done to date are just educated guesses based on markings on the existing componants. I've replaced the electrolytics and a toasted resistor in the power supply section (the resistor was burned in two, so I just made my best guess on a replacement). The radio plays loud and clear on AM, but after an hour or more it suddenly loses signal. On the FM side, the lower frequencies are a little weak when the set is cold and the higher freqs are fine. After just a few minutes of warming up, starting with the lower freqs the progressing up, it begins to lose signal across the entire FM band. So, does anyone have a suggestion on where I can find any information on this model or where I should concentrate my efforts on the troubleshooting? Even being able to find a schematic for another make / model radio with the same tube line up might be helpful (17EW8, 12BE6, 12AC6, 2 ea. 12BA6 & 50EH5).
Thanks,
Dave
Posts: 2,128
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Joined: Oct 2008
City: Merrick, Long Island, NY
Did you replace the rest of the capacitors?
I assume this is a printed circuit board and you would have cleaned it up with deoxit or tuner spray, so you you can go over the traces and connections to the tube sockets.
Poke around gently with a non conductive tool (I use a chopstick) and see if you can get it to cut out or back in.
Measure the resistors and replace all that are more than 20% off. They all usually drift high after decades. If I have to unsolder one end of a resistor to measure it out of circuit, I usually replace it anyway.
You also might have a silver mica capacitor that is bad. The dreaded mica disease is notorious for this. These will test OK on a digital meter, but will not pass muster when voltage is applied with an old fashioned condenser tester is used. Getting to them can be a real chore, especially if they are in the IF cans. Again, if I have to spend a half hour getting to them I just replace them.
Well that's a start. Good Luck
Posts: 91
Threads: 9
Joined: Feb 2010
City: Macon, GA
No printed circuit board, nothing but ceramic disk capacitors (other that the electrolytics) and tube sockets have been cleaned. The resistor that I replaced is now discolored from heat, so I'm pretty sure that it's the wrong value. Looks like as good of a place to start as any.
Thanks,
Dave
Posts: 217
Threads: 40
Joined: Dec 2009
Is this your set
http://www.radiomuseum.org/r/sansei_hi_mood.html When looking for info on this set drop the polaris .
Posts: 217
Threads: 40
Joined: Dec 2009
